.TH std::match_results::operator[] 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::match_results::operator[] \- std::match_results::operator[]

.SH Synopsis
   const_reference operator[]( size_type n ) const;  \fI(since C++11)\fP

   If n > 0 and n < size(), returns a reference to the std::sub_match representing the
   part of the target sequence that was matched by the n^th captured marked
   subexpression).

   If n == 0, returns a reference to the std::sub_match representing the part of the
   target sequence matched by the entire matched regular expression.

   if n >= size(), returns a reference to a std::sub_match representing an unmatched
   sub-expression (an empty subrange of the target sequence).

   The behavior is undefined unless ready() == true.

.SH Parameters

   n - integral number specifying which match to return

.SH Return value

   Reference to the std::sub_match representing the specified matched subrange within
   the target sequence.

.SH Example


// Run this code

 #include <iostream>
 #include <regex>
 #include <string>

 int main()
 {
     std::string target("baaaby");
     std::smatch sm;

     std::regex re1("a(a)*b");
     std::regex_search(target, sm, re1);
     std::cout << "entire match: " << sm[0] << '\\n'
               << "submatch #1: " << sm[1] << '\\n';

     std::regex re2("a(a*)b");
     std::regex_search(target, sm, re2);
     std::cout << "entire match: " << sm[0] << '\\n'
               << "submatch #1: " << sm[1] << '\\n';
 }

.SH Output:

 entire match: aaab
 submatch #1: a
 entire match: aaab
 submatch #1: aa

.SH See also

   str returns the sequence of characters for the particular sub-match
       \fI(public member function)\fP
